JPH03213365A - line printer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a line printer using electrophotography.

2. Description of the Related Art In recent years, line printers are one of the printers developed using electrophotography.

This line printer is one in which devices such as a charger, a line head, a developer, a transfer device, and the like are arranged facing each other on the circumferential surface of a photosensitive drum. Then, an electrostatic latent image is formed on the circumferential surface of the photosensitive drum charged by the voltage applied by the charger by selectively emitting light from a light emitting element connected to the line head. Printing is performed by developing the image with toner supplied from a developing device and transferring it onto printing paper using a transfer device.

The light emitting element of the line head as mentioned above is LED (
Light-emitting diodes) are currently used, but this has problems such as the difficulty of correcting differences in light emitting intensity between each element, so edge-emitting diodes are currently used as light-emitting elements for line heads. E L (
It has been proposed to use an E 1 electro Luminescence) element. Therefore, a line head using such an edge-emitting type EL element will be explained based on FIGS. 3 and 4. As illustrated in FIG. 4, the edge-emitting EL element 2 of this line head 1 has a thin active layer 3 made of zinc sulfide or the like containing an active element surrounded by dielectric layers 4 and 5 from above and below. Flat plate electrodes 6 and 7 are formed on the upper and lower surfaces of the dielectric layers 4 and 5, and extremely flat light is emitted from the end surface of the active layer 3, unlike the conventional E in which the upper surface emits light.
It is possible to obtain a luminescence intensity about 100 times that of L.

Then, as illustrated in FIG. 3, the line head l is formed by continuously forming the edge-emitting type EL elements 2 having the above structure using thin film technology and attaching a rod lens array (not shown), etc. be done.

Therefore, by connecting a drive circuit to the line head 1 having the structure described above and arranging it along with a charger, developing device, transfer device, etc. on the circumferential surface of the photosensitive drum, which is a photosensitive member, an electrophotographic line A printer (not shown) can be manufactured.

Various types of driving methods can be considered for the line head l as described above, but as illustrated in FIG.
, ~8m and n block electrodes 9, ~9n in a matrix, and applying synchronously controlled high-voltage and low-voltage drive pulses to these electrodes 8.9 to drive the line head 1 in a matrix. did.

Furthermore, the present applicant has disclosed an example of a specific method for driving the line head 1 as described above in Japanese Patent Application No. 1-97081. This corresponds to the fact that the beam shape of the emitted light from the edge-emitting type EL element 2 is flat, and as illustrated in FIG. 6, the time T required to form one main scanning line.

A plurality of drive pulses are applied to the line head 1 during the process, so that one pixel is formed by a plurality of light emitting operations. By doing this, the flat pixel components formed by one emitted light of the edge-emitting type EL element 2 are arranged consecutively in the sub-scanning direction, so that a substantially square pixel component is formed as shown in FIG. Pixels are obtained, the edges of the main scanning lines are also smoothed, and pixels can be formed with high print quality.

Problems to be Solved by the Invention By doing the above, a high-performance line printer (
) can be obtained.

Here, in such line printers, the photosensitive characteristics of the photoconductor and the line head 1 may vary due to manufacturing errors and aging.
The output characteristics of the product may differ from the design value.
In this case, the amount of toner adhering to each pixel may increase or decrease, resulting in a decrease in print quality.

Furthermore, in Japanese Patent Application No. 1-97085, the present applicant has proposed an intermediate method in which the number of light emitting operations of each edge-emitting EL element 2 is adjusted to arbitrarily reduce the number of pixel constituent elements forming one pixel. He also proposed a method for expressing the key.

As illustrated in FIG. 8, such a line printer 10 includes a drive circuit 11 in which the line head 1 is wired in a matrix with m common electrodes 8, 8m and n block electrodes 9, 9n. Light emission control circuit 12 as pixel forming means
A printing pattern memory 13, which is a part of a halftone expression means, is connected through the line head 1, and a photosensitive drum 14, which is a photosensitive member whose peripheral surface moves relatively in sub-scanning, is provided on the optical axis of the line head 1. It can be carried out with In this case, for example, if one pixel is formed by four light emitting operations, 2-bit density data is set in the print pattern memory 13,
According to this concentration data, the light emission control circuit 12 controls the drive circuit 1.
1 is controlled. Therefore, the edge-emitting type E
The light emission operation of L element 2 is performed when the concentration data of nibit is [0,
When Ol and [1,l:l, there is no light emission and full light emission, respectively, and when [0,I] and (1,Ol, light emission is made twice or three times, the intermediate concentration can be set. The pixels to be represented are printed.

Note that the line head 1 of such a line printer 10
As illustrated in FIG.
This can be implemented by applying this to each edge-emitting type EL element 2 of the line head 1, and making this combined pulse a driving pulse vPtvs of the edge-emitting type EL element 2 having a threshold voltage V78 or higher and lower than or equal to 78.

As illustrated in FIG. 10, the edge-emitting type EL element 2 driven in this manner has a threshold voltage vT□
Although the output characteristic shows a large change in the vicinity and then gradually stabilizes, the optical output still increases and decreases in response to the voltage of the drive pulse.

Further, in this line printer 10, for example, when the voltage of the drive pulse is V, =V, the amount of light received by the photosensitive drum 14 due to one light emission operation of the edge-emitting EL element 2 is 1.0 (μJ
/d), then by varying the four light emitting operations that form - pixels, the average amount of light received in one pixel area on the photosensitive drum 14 and the The average potential can be changed. Then, photosensitive drum 1
Since the amount of toner that corresponds to the average potential of the surface adheres to 4, this line printer IO realizes gradation expression in which the printing density of one pixel is set to four gradations, as illustrated in Table 1 below. be able to.

Table 1 The line printer 10 as described above enables gradation expression by varying the number of light emitting operations that form one pixel. However, in the line printer 10 having such a structure, as illustrated in FIG. 11(b), when the photosensitive characteristics of the photosensitive drum 14 change due to manufacturing errors or aging, one pixel on the photosensitive drum 14 changes. Since the average potential in the area changes with respect to the average amount of light received, as illustrated in the same figure and Table 2 below, the potentials representing gray 1 to black may be close to each other and the difference may be small. Occur.

Table 2 In the above case, each gray pixel and each black pixel become approximately the same color, hindering gradation expression and reducing the reproducibility of intermediate density.

Means for Solving the Problems The invention according to claim 1 provides a line head in which light emitting elements whose emission intensity changes in response to the voltage of driving power are arranged in an array, A photoreceptor whose scanning surface moves relatively in sub-scanning is provided, a drive circuit is provided that applies variable voltage drive power to the line head,
A pixel density changing means is provided to changeably set the voltage of the driving power output by the driving circuit.

The invention according to claim 2 provides a line head in which light emitting elements whose emitted light has a flat beam shape and whose emission intensity changes in accordance with the voltage of driving power are arranged in an array, and each light emitting element of this line head The number of pixel components in the pixel area is reduced by providing a pixel forming means that forms pixels by arranging flat pixel components formed on the scanned surface of the photoreceptor in the sub-scanning direction using the emitted light of A halftone expression means for forming pixels of intermediate density is provided, and a halftone adjustment means is provided for freely setting the voltage of drive power output by the drive circuit.

The invention according to claim 1 provides a line head in which light emitting elements whose emission intensity changes in accordance with the voltage of driving power are arranged in an array, and at least the surface to be scanned is relative to the line head. A photoconductor that moves in the sub-scanning direction is provided, and a drive circuit that applies variable voltage drive power to the line head is provided.
By providing a pixel density changing means that can freely change the voltage of the drive power output by this drive circuit, the photosensitive characteristics of the photoreceptor and the output characteristics of the line head may differ from the design values due to aging or manufacturing errors. Even if the values are different, the average potential in one pixel formed on the scanned surface of the photoreceptor can be corrected to the design value and the path value by increasing or decreasing the optical output of the line head. High-quality printing can be easily achieved.

The invention according to claim 2 provides a line head in which light emitting elements whose emitted light has a flat beam shape and whose emission intensity changes in accordance with the voltage of driving power are arranged in an array, and each light emitting element of this line head The number of pixel components in the pixel area is reduced by providing a pixel forming means that forms pixels by arranging flat pixel components formed on the scanned surface of the photoreceptor in the sub-scanning direction using the emitted light of By providing a halftone expression means to form pixels of intermediate density, and a halftone adjustment means to freely set the voltage of the drive power output by the drive circuit, the photoconductor Even if the photosensitive characteristics and output characteristics of the line head differ from the design values, the average potential in one pixel formed on the scanned surface of the photoreceptor can be adjusted to the design value by increasing or decreasing the optical output of the line head. Since the image can be corrected to the path-to-line value, it is possible to easily realize halftone printing with good reproducibility.

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 and 2. First, in the line printer 15 of the present invention, it is a pixel density changing means that freely sets the voltage of the drive pulse output from the drive circuit 11 to the line head 1 in the light emission control circuit 12, which is a pixel forming means, and is used for halftone adjustment. A dip switch 16, which is also a means, is connected.

In such a configuration, this line printer 15:
Printing expressing halftones is performed in the same manner as the line printer 10 described above.

In this line printer 15, when the dip switch 16 is turned on or off, the voltage of the drive pulse applied from the drive circuit 11 to the line head 1 is changed.

Therefore, in this line printer 15, the dip switch 16 is normally kept in the on state, and as illustrated in FIG. 2(a) and Table 3 below, one pixel of approximately square To satisfactorily perform halftone printing with four gradations of printing density.

Table 3 In this line printer 5, when the photosensitive characteristics of the photosensitive drum 14 become different from the designed values due to manufacturing errors or aging, the deep switch 16
is turned off, and the voltage of the drive pulse applied from the drive circuit 11 to the line head 1 is changed. Then, for example, the light output of the line head 1 is reduced, and as illustrated in FIG. 2(b) and Table 4 below, the photosensitive drum 14 is
Since the average amount of light received in the upper pixel area decreases, the average potential is corrected to the normal design value and the distance value.

Table 4 Therefore, this line printer 5 can maintain good reproducibility of intermediate density even if the photosensitive characteristics of the photosensitive drum 14 are different.

Note that the arrangement of pixel components provided in a pixel value expressing an intermediate density can be continuous or sporadic.

Further, although the line printer 15 of this embodiment maintains good reproducibility of halftone printing by changing the voltage of the drive pulse applied to the line head 1, the present invention is limited to the above method. For example, the present invention is applicable to a line printer (not shown) that performs printing using self-heating binary pixels.

In other words, if the photosensitive characteristics of the photoconductor or the output characteristics of the line head differ from the designed values due to aging or manufacturing errors, the voltage of the output pulse of the drive circuit is increased or decreased by operating the pixel density changing means. This makes it possible to easily adjust the optical output of the line head and perform high-quality black and white printing.

Effects of the Invention The invention described in claim 1 provides a line head in which light emitting elements whose emission intensity changes in accordance with the voltage of driving power are arranged in an array, and at least a surface to be scanned is relative to the line head. A photoreceptor is provided that moves in the sub-scanning direction, and a drive circuit is provided that applies variable voltage drive power to the line head.
By providing a pixel density changing means that can freely change the voltage of the drive power output by this drive circuit, the photosensitive characteristics of the photoreceptor and the output characteristics of the line head may differ from the design values due to aging or manufacturing errors. Even if the values are different, the average potential in one pixel formed on the scanned surface of the photoreceptor can be corrected to the design value and the path value by increasing or decreasing the optical output of the line head. A line printer with high printing quality and stable performance can be easily obtained, and the invention according to claim 2 uses a light emitting element with a flat beam shape of emitted light and whose emission intensity changes in accordance with the voltage of driving power. Line heads are arranged in an array, and pixels are formed by arranging flat pixel components in the sub-scanning direction, which are formed on the scanned surface of the photoreceptor by the light emitted from each light emitting element of the line head. A pixel forming means is provided, and a halftone expressing means is provided for forming a pixel of intermediate density in which the number of pixel constituent elements in the pixel area is reduced;
By providing a halftone adjustment means that can freely change the voltage of the drive power output by the drive circuit, it is possible to prevent the photosensitive characteristics of the photoconductor and the output characteristics of the line head from differing from the designed values due to aging or manufacturing errors. Even if the average potential in one pixel formed on the scanned surface of the photoreceptor can be corrected to the design value and the path-to-line value by increasing or decreasing the optical output of the line head, the intermediate This has the advantage that it is possible to easily obtain a line printer with good tone printing reproducibility and stable performance, and it can contribute to improving the performance of various line printers.

4,

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a characteristic diagram of a photosensitive drum, FIG. 3 is a perspective view showing a line head, FIG. 4 is a perspective view showing an edge-emitting type EL element, and FIG. Figure 5 is a circuit diagram showing the wiring structure of the line head proposed by the applicant, Figure 6 is a time chart of drive pulses, Figure 7 is a plan view of a printed image, Figure 8 is a block diagram, and Figure 9 is a diagram. A time chart of drive pulses, FIG. 10 is an output characteristic diagram of the edge-emitting type EL element, and FIG. 11 is a characteristic diagram of the photosensitive drum. 1... line head, 2... edge emitting type EL element,
11...Drive circuit, 12...Pixel forming means, 13...
・Halftone expression means, 14... Photoreceptor, 15... Line printer, 16... Pixel density changing means and halftone adjuster - Atsushi Figure 5 Ichida Mokko + (>April G. Part! 3 3,!

Claims (1)

[Claims] 1. A line head in which light emitting elements whose emission intensity changes in accordance with the voltage of driving power are arranged in an array, and at least a surface to be scanned is sub-scanned relative to the line head. It is characterized by comprising a moving photoreceptor, a drive circuit that applies voltage-variable drive power to the line head, and pixel density changing means that freely sets the voltage of the drive power output by the drive circuit. line printer. 2. A line head is provided in which light emitting elements whose emitted light beam shape is flat and whose emitted light intensity changes in accordance with the voltage of the driving power are arranged in an array, and the emitted light from each light emitting element of this line head is used to illuminate the photoreceptor. A pixel forming means is provided for forming pixels by arranging flat pixel constituent elements formed on a scanned surface in the sub-scanning direction to form pixels of intermediate density with a reduced number of pixel constituent elements in the pixel area. 2. The line printer according to claim 1, further comprising: a halftone expressing means for outputting an image, and a halftone adjusting means for freely setting the voltage of the drive power output by the drive circuit.